Teddy knows the sound of the microwave beeping. He knows that means food. Even if it's just the timer, he gets all excited.

Teddy also recognizes the difference in footsteps. If you walk differently (or it's someone he doesn't know), he'll bark wildly.

All the cats and dogs recognize my truck's sound. They get all excited and wait for me when I get home.

Of course, everyone also knows the sound of food hitting the dish.